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. Author manuscript; available in PMC: 2015 Apr 27.
Published in final edited form as: J Am Chem Soc. 2013 Aug 27;135(36):13456–13463. doi: 10.1021/ja4053398

Figure 4.

Figure 4

The three ClyA-CS nanopores. (a) Current-voltage (I-V) curves for Type I (red), Type II (blue) and Type III (green) ClyA-CS pores. The I-V curve of Type III ClyA-CS shows ionic currents sampled at potentials lower than ±100mV due to the instability of the pore at higher applied potentials. (b) Current recordings of Type I (top) and Type II (middle) ClyA-CS at −150 mV and Type III ClyA-CS (bottom) at −35 mV. (c) Current power spectral densities of the Type I (red), Type II (blue) and Type III (green) ClyA-CS nanopores at −35 mV obtained from 0.5 s traces showing the low frequency noise in ClyA-CS nanopores. The current power spectral density at 0 mV is shown in black. Each line corresponds to the average of power spectra calculated from 3 recordings carried out on different single channels. (d) Section through the molecular models corresponding to the 12mer, 13mer and 14mer ClyA nanopores. The proteins are shown as surface representations and colored according to their “in vacuum” electrostatics (red for negative regions, and blue for positive regions, Pymol). The blue and yellow boxes (left) describe the theoretical cylinders corresponding to the cis vestibule and transmembrane region (trans vestibule), respectively, that are used to model the conductance of ClyA in equation 2. Recordings were carried out at −35 mV, 28° C in 15 mM Tris.HCl pH 7.5 containing 150 mM NaCl. The I-V current traces were recorded with an automated voltage protocol that applied the desired potential for 0.4 seconds. Electrical recordings were carried out at 28° C in 15 mM Tris.HCl pH 7.5 containing 150 mM NaCl.